Beyond Glaciers: Yosemite's Big Trees Disappear

A man stands in front of a centuries-old tree in Yosemite National Park. Photo by Buddhika Gammudali via Flickr.com.

There's no denying the splendor of the giant trees that grace the west coast. But even giants aren't impervious to climate change, it seems.

Just as Yosemite's glaciers are disappearing, so too are the trees. An examination of data collected from the 1930s to 1990s has revealed that the numbers of giant, old-growth trees in Yosemite National Park have dropped dramatically during the 60-year span--and that worries researchers. If climate change isn't the only cause of this thinning of the forest, a recent BBC article reveals the research team considers it an "important driver."

Yosemite Tree Numbers CollapseUniversity of Washington researchers James Lutz and Jerry Franklin, along with Jan van Wagtendonk of the Yosemite Field Station of the U.S. Geological Survey, studied data collected between the 1930s and 1990s, with an emphasis on two comprehensive surveys from the '30s and '90s.

They discovered the density of trees in Yosemite National Park declined considerably over the course of 60 years--by a shocking 24 percent. Of the 14 species studied, the forest density of 11 declined.

Lutz told the BBC he was surprised at these findings because these centuries-old trees have weathered dry and wet periods without fail. In fact, the discovery casts aside assumptions that old trees are better able to adapt to changes in the environment, such as the changes that have come with the higher temperatures associated with climate change.

But there's another cause for concern as well. As Lutz told the BBC,

One of the most shocking aspects of these findings is that they apply to Yosemite National Park. Yosemite is one of the most protected places in the US. If the declines are occurring here, the situation is unlikely to be better in less protected forests.

Why a Prolific Yosemite National Park Matters

Old trees play a crucial role in forest ecosystems. They provide seeds for new growth, and some animals also rely on seeds for survival. But they also consume a lot of water, solar energy and nutrients--take them away and we could have a big problem on our hands. As Lutz puts it,

...what the consequences could be of a decline in average large tree diameter, no-one really knows.